Centrifugal casting machine



.July 16, 1935.

K. WEBER CENTRIFUGAL CASTING MACHINE Filed April 7, 1933 an M a/a Patented July 16, 1935 UNIT'D STATES PATENT OFFICE Application April I, 1933, Serial No. 685,016

In Germany Aprll 13, 1932 1 Claim. (CI. 22-65) The production of rolls from so-called compound castings, that is, of a hardened shell of special material against wear for the working surface and an inner softer core of a softer in- 5 set, either of cast iron or steel for protection against breakage, has been in recent years repeatedly striven for and already carried out in different ways.

It is also known to cast compound bodies, in

particular rolls, of several metals in such centrifugal casting moulds as only rotate about the perpendicular axis, the jacket 'metal being first cast and then the core metal. This process has, however, the disadvantage that the jacket metal 5 sinks down and consequently does not form anything approaching a uniform thickness of wall of the jacket. For these reasons, it has been preferred to generally cast the jacket with a mould lying horizontally, and then to fill in the core metal with the mould standing perpendicularly.

But all these processes which first centrifuge the outer jacket in the horizontal position and then rotate the machine into the vertical posia different metal, either in centrifugal casting or in stationary position, so combining it with the harder jacket already formed, start from wrong premises and have not yet shown in practice that they can be carried out, which in all probability will never be the case if the following facts are considered.

Assuming that the outer jacket has been first independently centrifuged horizontally, it cannot be brought into the perpendicular position until it is suificiently solidified, as otherwise it would collapse. If, however, the solidification be first awaited, then afterwards there can never take place between the jacket already solidified to a certain extent and the softer material afterwards poured in, the intimate combination or welding which is necessary in order to prevent a later complete or partial displacement of the outer jacket from the inner soft core. In order to obviate this possibility or danger, it has already been suggested to remove any slags which may have collected inside the jacket by means of a stripper and to insert special pins or frames or a chemical medium between the jacket and the core and 50 centrifuge this in, in order to obtain some connection between the outer jacket and the inner core.

Apart from all the disadvantages of these processes in practice, the danger and the cost of such a method of working with comparatively heavy tion in order to cast the inner softer core out of bodies such as rolls must not be left out of consideration.

In this invention the outer jacket is first independently cast whereby I am able according to the quantity poured in to centrifuge the outer jacket in any desired thickness. The simplicity of my process, furthermore, consists in that the machine continues to run in the same position, and from a second ladle held ready the inner core of softer materialis poured in and cen: trifuged at the moment when the inner surface of the previously centrifuged jacket, already solidified on the outer surface, is still so liquid or pasty that a perfectly homogeneous combination between the outer hard jacket and the inner soft 1 core takes place, as practical tests carried out by me have shown.

While the German Patent No. 519,237 of which I am aware only refers to the production of metal hollow bodies in particular form ingot iron and 20 steel, in continuous casting in perpendicular rotating chill moulds, the speed of rotation being gradually and uniformly increased during the pouring in and being brought after this pouring in has terminated, to a maximum, with my process it is a matter primarily of the production of solid bodies such as rolls in rotating chill moulds, into which the metal is only poured when the mould has reached the maximum speed previously calculated according to the dimensions of the mould and the properties of the metal, I being able, however, to centrifuge hollow rolls also ao- 'cordlng to the same principle. This maximum speed of rotation is maintained until a considerable part of the second metal is poured in, so that it forms a retaining wall for preventing the jacket first centrifuged from collapsing. Immediately this retaining wall is formed and a welding together of the two materials (which are still fluid) has taken place, the maximum speed of rotation is gradually reduced downto a minimum speed which has been previously calculated to be such as will produce a casting which, including the trunnions, is not hollow.

In the same way, the American Patent No. 1,533,780 of which Pam aware, only calculations are shown which represent purely parabolic constructions from which later on the desired bodies can be machined. with my process, on the other hand, the prepared cylindrical jacket is formed with only the very slightest sign of this parabolic shape and without subsequent working.

In order to obviate the defect of the inner part of the hollowbody first centrifuged having the contour of a rotation paraboloid so as to involve machining, in my intention a practically rectilinear limiting line of the inner wall is attained by regulating the speed in dependence on the dimensions of the centrifugal casting chill mould as also in taking into consideration the properties of the kind of metal cast, which rectilinear line can be made cylindrical or also conical as desired. This problem is solved by the jacket metal being poured in when the speed of mould rotation is such as will produce the substantially cylindrical shape of the inner surface of the jacket. bearing in mind the speed of solidification and the other physical properties coming into question of the metal being cast. For example, with a roll of 600 mm. diameter and 1,000 mm. length of working surface, a speed of rotation of 800 revolu tions per minute would be necessary. In the casting of the core, the speed ofrotation is proportionally reduced, and in this case brought to a final speed of rotation of 200 per minute. According to my process, both so-called chill mould rolls, and also steel rolls and naturally also those of non-ferrous metals, may be centrifuged from two different metals. with the chill mould rolls the outer jacket consists preferably of a mixture as hard as possible with about 4 to 4.5 0., 1.5 to 2.5 Mn., 1.25 to 1.5 81, 0.5 to 1.5 Cr. 1.5 to 25 Ni, and with steel roll jackets, preferably of chrome nickel steel, while the inner core as protection against danger of breaking with cast iron rolls is made of softer grey iron, or better still, cast steel, and with steel rolls also of a soft tough cast steel. The temperature of the hard jacket first centrifuged should be as high as possible in the case of chilled cast rolls at about 1400 to 1500 and in the case of steel rolls at about 1600 to 1700 in order to obtain a good welding with they inner core material cast at a slightly lower temperature. With rolls made of non-ferrous metals, the outer jacket may consist of copper or a hard bronze and the inner core of a tough brass.

The objection that after the casting or centrifuging of the outer jacket any particles of slag present on the inner surface thereofv form holes in the welding zone and consequently do not permit of a perfect intimatefconnection or weld between the material of the jacket and of the core, has with my process no practical impor-' able to pass into the material, actually particles of slag should be present on the inner surface of the jacket these are carried away by the stream' of the second material poured in beforetheflnal solidification of the outer jacket and deposited inside the core or above in the funnel, as with my process the second material is poured in and centrifuged at the moment jwhenthe inner surface of the previously centrifuged jacket already solidified on the outer surface, isstill .suiliciently liquid, and consequently carries away with it in its streamany actually existing particles of slag, into the interior of the core. or upwards into the funnel. This has been proved perfectly with my process by practice as being the best instructor.

Even if not actually necessary, a distributing device at the bottom of the mould is advisable, consisting of a number of curved channels branching out from the centre point of entrance of the metal and curved in the direction of rotation, of the centrifugal casting mould, through which channels is supplied primarilythe Jacket metal but also afterwards so far as is practicable, the other metal serving for the formation of the layers following on to the jacket.

In German Patent No. 544,319 mention is al- 5 vice it is a question of channels curved in the direction of rotation of the centrifugal casting mould and the eifect of which channels is quite a diflerent one.

My process also permits the making of the roll trunnion in soft material in the same chill mould as compared with the otherwise usual tedious separate preparation of the trunnions in sand.

Also I am aware of the German Patent No. 539,816, but in this case only the jacket of the casting is to be produced by centrifugal casting with a horizontal position of the mould, while the core of the casting, consisting of a different material, and with it also the trunnion, are cast by the long known casting process in a stationary vertical position of the mould by upflow casting preferably with tangential entry of the material,

In the drawing appended herewith to illustrate go one form of my invention, Fig. 1 is a longitudinal section through the casting mould (chill mould) and roll.

Fig. 2 shows the distributing device a in plan.

The mould is set in rotation by the centrifugal machine a and the rotating plate a. 1 b is the mould, c the corresponding cover which is fixed by means of bolts and nuts on the flange of the mould b, (1 shows the outer hard roll jacket, c the inner soft core, I the combining or welding .zone between the jacket d and the core c. i shows an extension of the journal h in order to permit the solid casting of the journal h.

.In Fig. 2 the channels In curved in the direction of rotation of the mould show the inlet of the material poured in.

What I claim is:

In apparatus for use in the production of cylindrical or conical metal bodies in which an inher core is cast into an outer harder shell in a cylindrical or conical centrifugal casting mould rotating about a vertical axis, the use of a dis-- tributing device arranged in the bottom of the mould and consisting of a number of channels branching from the centre of the point of entry of the metal and curved in the direction of rotation of the centrifugal casting mould, through which channels both the outer shell metal and also the core metal are supplied, the arrangement being that the metal to form the shell is poured into the centre of the mould from above the mould when the mould has reached a predetermined high speed of rotation, being the minimum speed asdetermined by the dimensions of the mould that is necessary to produce an outer 65 shell which has an inner surface co-axial with the mould and nearly truly cylindrical in form, and the core metal is subsequently poured into the centre of this shell when the shell has solidifled externally but while still liquid or pasty 7o KARL WEBER.

internally. 

